prEN ISO 9225

SLOVENSKI STANDARD
01-maj-2026
Korozija kovin in zlitin - Korozivnost v atmosferskem okolju - Merjenje okoljskih
parametrov, ki vplivajo na korozivnost atmosfer (ISO/DIS 9225:2026)
Corrosion of metals and alloys - Corrosivity of atmospheres - Measurement of
environmental parameters affecting corrosivity of atmospheres (ISO/DIS 9225:2026)
Korrosion von Metallen und Legierungen - Korrosivität von Atmosphären - Messung der
die Korrosivität von Atmosphären beeinflussenden Umweltparameter (ISO/DIS
9225:2026)
Corrosion des métaux et alliages - Corrosivité des atmosphères - Mesurage des
paramètres environnementaux affectant la corrosivité des atmosphères (ISO/DIS
9225:2026)
Ta slovenski standard je istoveten z: prEN ISO 9225
ICS:
77.060 Korozija kovin Corrosion of metals
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

DRAFT
International
Standard
ISO/DIS 9225
ISO/TC 156
Corrosion of metals and alloys —
Secretariat: SAC
Corrosivity of atmospheres —
Voting begins on:
Measurement of environmental
2026-03-09
parameters affecting corrosivity of
Voting terminates on:
atmospheres
2026-06-01
Corrosion des métaux et alliages — Corrosivité des atmosphères
— Mesurage des paramètres environnementaux affectant la
corrosivité des atmosphères
ICS: 77.060
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENTS AND APPROVAL. IT
IS THEREFORE SUBJECT TO CHANGE
AND MAY NOT BE REFERRED TO AS AN
INTERNATIONAL STANDARD UNTIL
PUBLISHED AS SUCH.
This document is circulated as received from the committee secretariat.
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Reference number
ISO/DIS 9225:2026(en)
DRAFT
ISO/DIS 9225:2026(en)
International
Standard
ISO/DIS 9225
ISO/TC 156
Corrosion of metals and alloys —
Secretariat: SAC
Corrosivity of atmospheres —
Voting begins on:
Measurement of environmental
parameters affecting corrosivity of
Voting terminates on:
atmospheres
Corrosion des métaux et alliages — Corrosivité des atmosphères
— Mesurage des paramètres environnementaux affectant la
corrosivité des atmosphères
ICS: 77.060
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENTS AND APPROVAL. IT
IS THEREFORE SUBJECT TO CHANGE
AND MAY NOT BE REFERRED TO AS AN
INTERNATIONAL STANDARD UNTIL
PUBLISHED AS SUCH.
This document is circulated as received from the committee secretariat.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL,
© ISO 2026
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
STANDARDS MAY ON OCCASION HAVE TO
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Published in Switzerland Reference number
ISO/DIS 9225:2026(en)
ii
ISO/DIS 9225:2026(en)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Principle . 1
4 Humidity and temperature parameters . 2
4.1 Relative humidity .2
4.2 Temperature .2
5 Airborne contaminants . 2
5.1 Principle .2
5.2 Placement of measurement equipment .2
5.2.1 Continuous gas concentration measurement instruments .2
5.2.2 Measurement instruments with active sampler .3
5.2.3 Measurement instruments with diffusive sampler .3
5.2.4 Deposition rate equipment .3
5.3 Measurement methods and duration .3
5.3.1 Continuous measurement .3
5.3.2 Measurement with active sampler .3
5.3.3 Measurement with diffusive sampler .3
5.3.4 Measurement of deposition rate of pollution .4
Annex A (normative) Determination of sulfur dioxide deposition rate on lead dioxide sulfation
plates . 6
Annex B (normative) Determination of sulfur dioxide deposition rateon lead dioxide sulfation
cylinder . 9
Annex C (normative) Determination of sulfur dioxide deposition rate on alkaline surfaces .12
Annex D (normative) Determination of chloride deposition rate by the wet candle method. 14
Annex E (normative) Determination of chloride deposition rate by dry plate method .18
Annex F (normative) Comparison of chlorides and sulfur dioxide deposition ratesdetermined
by different methods .22
Annex G (normative) Comparison of chlorides and sulfur dioxide deposition ratesdetermined
by different methods .23
Bibliography .24

iii
ISO/DIS 9225:2026(en)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out through
ISO technical committees. Each member body interested in a subject for which a technical committee
has been established has the right to be represented on that committee. International organizations,
governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely
with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 9225 was prepared by Technical Committee ISO/TC 156, Corrosion of metals and alloys.
This third edition cancels and replaces the second edition (ISO 9225:2012), which has been technically
revised.
iv
ISO/DIS 9225:2026(en)
Introduction
The ability of an atmosphere to cause corrosion of metals and alloys is controlled by the following factors:
the temperature-humidity complex and pollution. A basic requirement for the estimation of the corrosivity
of atmospheres is standardized measurement of the important parameters describing the correlation
between the corrosion and the environmental characteristics.
The methods included in this International Standard have been chosen for their easy applicability and
good comparability of results. It is important to stress that the methods for estimation of the atmospheric
corrosivity given in ISO 9223 are based on the measurement methods described in this International
Standard.
v
DRAFT International Standard ISO/DIS 9225:2026(en)
Corrosion of metals and alloys — Corrosivity of atmospheres
— Measurement of environmental parameters affecting
corrosivity of atmospheres
WARNING — Some of the procedures included in this International Standard entail the use of
potentially hazardous chemicals. lt is emphasized that all appropriate safety precautions should be
taken.
1 Scope
This International Standard specifies methods for measuring the parameters needed for corrosivity
estimation used for classification of the corrosivity of atmospheres in ISO 9223.
This International Standard specifies methods for the measurement of environmental parameters for
— normative corrosivity estimation based on calculated first-year corrosion rates of standard metals, and
— informative corrosivity estimation based on characterization of the exposure environment.
This International Standard does not describe the usual analytical techniques for the measured parameters
since this depends on the available analytical techniques used in laboratories. Specific methods for
−
deposition measurement of SO and Cl deposition rates and conversion factors for comparison of different
measuring methods are presented in Annexes A, B, C, D, E and F.
For methods pertaining to the characterization of the atmospheric exposure site in general, see ISO 8565.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
ISO 9223, Corrosion of metals and alloys — Corrosivity of atmospheres — Classification, determination and
estimation
ISO 11844-3, Corrosion of metals and alloys — Classification of low corrosivity of indoor atmospheres — Part 3:
Measurement of environmental parameters affecting indoor corrosivity
3 Principle
Different environmental parameters and their combinations affect the corrosivity of the atmosphere. Two
methods for corrosivity estimation (normative and informative) are specified in ISO 9223.
In general, two groups of parameters are obtained or measured for standardized procedures of corrosivity
estimation:
— humidity and temperature;
— airborne contaminants.
Standardized corrosivity estimation is based on information on levels of the dominating environmental
parameters: the temperature-humidity complex, and pollution with SO and airborne chlorides.
Measurements of these parameters are mandatory for the purpose of corrosivity estimation.

ISO/DIS 9225:2026(en)
−
Contaminants other than SO and Cl , such as NO , O , H S, HNO , can also exert an effect on the corrosion
2 x 3 2 3
2− − −
rate. Corrosion active components of dust deposits (SO , NO , Cl ) react with metals in the presence
4 3
of humidity. These factors are considered as accompanying factors (see ISO 9223). These environmental
parameters, which contribute to the effect on corrosion of standard metals in multi-pollutant situations, are
not included as mandatory parameters for corrosivity estimation in ISO 9223. Information on levels of these
parameters can help in informative corrosivity estimation.
Methods for the measurement of environmental parameters to be used specifically for the estimation of low
corrosivity of indoor atmospheres (IC) are given in ISO 11844-3.
4 Humidity and temperature parameters
4.1 Relative humidity
Reliable long-term average values for relative humidity can often be obtained from the meteorological
authorities in the country. Several types of measuring devices can be used if collection of new data for the
locality is needed. There are several continuous measuring devices, such as hygrographs, thermohygrographs
or logging hygrometers, available on the market.
The period of measurement is preferably one year in order to cover seasonal variations and because the
classification system is based on yearly average values. The data shall be expressed as yearly mean values.
4.2 Temperature
Reliable long-term average values for temperature can often be obtained from the meteorological
authorities in the country. Several types of measuring devices can be used if collection of new data for the
locality is needed. There are several continuous measuring devices, such as thermohygrographs or logging
thermometers, available on the market.
The period of measurement is preferably one year in order to cover seasonal variations and because the
classification system is based on yearly average values. The data shall be expressed as yearly mean values.
5 Airborne contaminants
5.1 Principle
The gas concentration or deposition rate may be measured using several techniques:
— continuous gas concentration measuring instruments;
— average gas concentration with active sampler and air pump;
— average gas concentration with diffusive (passive) sampler;
— average deposition rate equipment.
The results from concentration measurements are typically given in micrograms per cubic metre (µg/m )
and, for deposition measurements, in milligrams per square metre per day [mg/(m ⋅d)].
5.2 Placement of measurement equipment
5.2.1 Continuous gas concentration measurement instruments
The instrument shall be located in a place that is sheltered from the rain and protected from unauthorized
people. Preferably, the instrument should be placed indoors with a tube leading out to the ambient air.
Polyethylene or PTFE tubing is recommended and the length of the tubing should not exceed 2 m. The inlet
shall be facing down with a wider hood at the inlet to reduce the risk of sucking particulates into the tube.

ISO/DIS 9225:2026(en)
5.2.2 Measurement instruments with active sampler
The active sampler equipment shall be placed according to the same rules as the continuous gas-measuring
instrument.
5.2.3 Measurement instruments with diffusive sampler
The sampling device shall be placed with the open end facing downward under appropriate shelter. The air
flow influences the gas diffusion in the sampler.
5.2.4 Deposition rate equipment
The equipment shall be sheltered from setting particles and from washing out by rain for outdoor deposition
measurements. The air flow influences the deposition rate.
5.3 Measurement methods and duration
5.3.1 Continuous measurement
The measurements shall preferably be carried out for one year in order to record the seasonal variation of
the gas pollutants. The data from continuous measuring instruments shall be recorded as monthly average
values. For the corrosivity estimation, the data shall be expressed as yearly mean values.
-9
Standard instruments have detection limits in the 10 volume fractions range.
5.3.2 Measurement with active sampler
The methods are based on pumping air through an absorption unit with a reactive surface or liquid, with
subsequent laboratory analysis of the amount absorbed. The flow rate is 0,18-0,22 L/min for 24 h sampling
time with an absorption solution of 50 mL. The sampling period shall be one week. The data shall be collected
over the sampling periods and summarized to monthly average values. The result is given as an average
concentration for the measuring period.
The measuring period is preferably one year or at least one month for each season of the year. For the
corrosivity estimation, the data shall be expressed as yearly mean values.
NOTE The detection limits for air concentrations depend on the sensitivity of the analysing instruments and the
duration of the sampling. For an analytical instrument with normal sensitivity, it is possible to obtain weekly average
values with a detection limit better than 0,1 µg/m .
5.3.3 Measurement with diffusive sampler
Mean gas concentrations can be calculated using diffusive sampling devices. The principle used for diffusive
sampling is shown in Figure 1. The recommended sampling period is one month, but can be extended to
three months, corresponding to one measurement for each season of the year. The measurement period is
preferably one year.
ISO/DIS 9225:2026(en)
Key
1 absorbent
2 tube
3 permeable screen for gases
C ambient concentration of gas
C concentration of gas at the absorbent equal zero
Figure 1 — Principle of concentration calculation for a diffusive sampler
NOTE Normal sensitivity for weekly mean values is down to 0,1 µg/m for SO , but higher for other gases.
Generally the detection limit decreases with increasing sampling time.
The general calculation model is specified in ISO 11844-3.
The data shall be expressed as yearly mean values.
5.3.4 Measurement of deposition rate of pollution
The deposition takes place on an absorbing or collecting surface similar to the surfaces used for diffusive
sampling devices. In the deposition method standardized for SO deposition measurements, the gas reacts
when it reaches the lead dioxide surface or alkaline surface (see Annexes A, B and C). In the methods
standardized for airborne salinity measurements, particles (aerosol) are deposited on a wet or dry surface
designed to collect this pollutant (see Annexes D and E). Since the collecting system is open, the deposition
rate depends on the movement of the air.
NOTE The use of lead compounds can be restricted in some countries.
SO deposition measurements performed by the lead dioxide plates and by the lead dioxide cylinder
differ with regard to the kind and shape of the deposition surface. Both measurements give values with
low correlation for monthly sampling periods due to the greater variation in weather characteristics.
A high correlation exists for annual average values (see Annex F). Capture of sulfuric acid aerosols and
sulfur-bearing species from precipitation and sea salt deposition can occur.
The SO deposition values used for the derivation of the dose-response functions given in ISO 9223 are
either based on deposition measurements on alkaline surfaces or converted values based on concentration
measurements.
Chloride deposition rates determined by the dry plate method and by the wet candle method differ because
the kind and shape of deposition surface are different (wet/dry surfaces, cylindrical/plate format of the
deposition surface). There is little difference in the deposition rates determined by the two methods at
locations with very low deposition rates, i.e. <10 mg/(m ⋅d). On the other hand, at the locations with chloride
deposition rates in the range of 10 to 100 mg/(m ⋅d) , the wet candle method gives deposition rates that are
approximately twice as high as those given by the dry plate method (see Annex F).
The chloride deposition values used for the derivation of the dose-response functions given in ISO 9223 are
based on measurements with the wet candle method. If the chloride deposition is measured with the dry

ISO/DIS 9225:2026(en)
plate method (see Annex E), it is necessary that the transformation factor given in Annex F be applied before
using the dose-response functions.

ISO/DIS 9225:2026(en)
Annex A
(normative)
Determination of sulfur dioxide deposition rate on lead dioxide
sulfation plates
A.1 Principle
Atmospheric sulfur dioxide (SO ) reacts with the lead dioxide (PbO ) to form lead sulfate (PbSO ). The plates
2 2 4
are withdrawn after exposure and sulfate analysis is performed on the contents to determine the extent of
sulfur dioxide capture. The deposition rate of sulfur dioxide is expressed in milligrams per square metre per
day [mg/(m ⋅d)].
The lead dioxide reagent used in this method can also convert other sulfur-bearing compounds, such as
hydrogen sulfide (H S) and mercaptans (C H SH), to sulfate.
2 2 5
The inverted position of the disc is intended to minimize sulfur capture from acid precipitation or sulfuric
acid (H SO ) aerosols.
2 4
A.2 Sampling apparatus
A.2.1 Sulfation plate
Sulfation plates may be purchased ready for exposure or may be prepared. The following method is
recommended for the preparation of sulfation plates.
Bond filter paper circles to the bottom of polystyrene Petri dishes. The circle diameters may be 50 mm or
60 mm. Bonding is carried out by placing a filter paper rough side up, in the bottom of the dish. The filter
paper should fit inside the dish without wrinkling. Carefully squirt acetone into the dish so that the filter
becomes just saturated. Press the filter paper firmly with a glass rod so that it adheres completely to the
dish. Allow the acetone to evaporate. The operation should be conducted in a fume hood to prevent the
direct release of acetone into the atmosphere.
Place a batch of bonded plates (several tens of either 50 mm plates or 60 mm plates) in a rack and rinse with
distilled or demineralized water. Fill the plates with water again and allow to stand for 1 h. Pour the water
out of the plates and re
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